It is generally known in the art, that polyelectrolytes are suitable for surface precipitation from the solution, i.e. for forming layers or coatings on a surface. For example WO-A-02/09865 discloses a method of producing nano- or microcapsules comprising a polyelectrolyte casing by surface precipitation from the solution onto the surface of template particles.
Many devices used in biomedical applications require that the bulk of the device has one property, while the surface of the device has another property. For example, contact lenses may have high oxygen permeability through the lens to maintain good corneal health. However, materials that exhibit exceptionally high oxygen permeability (e.g. polysiloxanes) are typically hydrophobic and will adhere to the eye. Thus, such a contact lens generally has a core or bulk material that is highly oxygen permeable and hydrophobic, and a surface that has been treated or coated to increase hydrophilic properties, thereby allowing the lens to freely move on the eye without adhering.
As a result, a number of methods of consistently and permanently altering the surface properties of contact lenses, have been developed.
WO-A-99/35520 discloses a layer-by-layer (“LbL”) polymer absorption process comprising the steps of consecutively dipping a substrate into oppositely charged polyionic materials until a coating of a desired thickness is formed.
WO-A-01/57118 discloses a method for forming a coating of polyionic material on a contact lens by dipping the contact lens into a (single) solution containing a polyanionic material and a polycationic material in a non-stoichiometric amount and maintained within a certain pH-range.
U.S. Pat. No. 6,451,871 discloses a method for coating an ophthalmic lens in the primary package comprising the steps of forming a polyionic coating solution comprising a negatively and/or positively charged polyionic material; contacting an ophthalmic lens with said solution in the primary package for said lens; forming a coating on said ophthalmic lens, said coating comprising said charged material; and maintaining said lens in said package with the remaining after-solution until insertion of the lens in the eye of the ophthalmic lens user.
All prior art approaches so far comprise several handling steps, including preconditioning, dipping, rinsing and thereafter packaging.
As such, a need currently exists for an improved method of coating a material, such as an ophthalmic lens, preferably a contact lens, with polyelectrolyte coatings (i.e. polyionic coatings). In particular, a need exists for an improved polyionic deposition technique that requires less manufacturing time and handling steps than the previously-described layer-by-layer deposition technique.